Means for counterbalancing starting thrust in turbine driven pump units



Dec. 30, 1958 J. G. WILLIAMS 2,866,620 MEANS FOR COUNTERBALANCINGSTARTING THRUST IN TURBINE DRIVEN PUMP UNITS Filed Oct. 3, 1957 JOHN G.WILLIAMS INVENTOR.

MEANS FOR COUNTERBALANCING STARTING THRUST IN TUINE DRIVEN PUMP UNITSJohn G. Williams, Springfield, N. J., assignor to WorthingtonCorporation, Harrison, N. J., a corporation of Delaware ApplicationOctober 3, 1957, Serial No. 688,041

1 Claim. (Cl. 25365) This invention generally relates to improvementsfor turbine-driven pump units, and more particularly relates to meansfor counterbalancing the starting thrust load of these units caused bystatic fluid pressure in the pump, to thereby eliminate considering thisfactor in the selection of a thrust bearing appropriate for the unit.

It is the common practice today to use a large and expensive bearingwhenever a large thrust load must be overcome in starting the pumpingunit. This practice, however, creates waste because in subsequentoperations, a hydrodynamic oil film will be developed by rotation underthe bearing pads or bearing surfaces, and the load-carrying capacity ofthe bearing increased to a greater extent than is needed, whereby thebearing is more expensive than one that could efiectively handle thenormal thrust load requirements of the unit.

Accordingly, to eliminate this waste, it is an object of the presentinvention to provide the pumping unit with suitable means tocounterbalance the starting thrust load, thereby permitting the thrustbearing to be selected independently of this factor, and thus inaccordance with its expected normal operational thrust loadrequirements.

It is a further object to provide the means for counterbalancing thestarting thrust load by adapting the usual elements of the turbine tothis purpose, whereby no additional expense is incurred.

More specifically, as is usual in steam turbines, running clearance isprovided between the sides of the turbine wheel and the walls of thesteam chamber, and at the periphery of the running clearance on one sideof the turbine wheel, the flow directing nozzles mounted about the steamchamber wall are positioned within close proximity of the steam bucketscarried about the periphery of the turbine wheel. The close proximitybetween the buckets and nozzles is required for eflicient operation ofthe turbine and has been found to constitute a natural restriction toany radially outwardly flowing steam from the running clearance spacebetween the turbine wheel and steam chamber wall. Thus, this saidrunning clearance space effectively serves as a steam chamber, and toaccomplish the objects of the present invention, high pressure steam isadmitted through a suitable inlet to this chamber prior to starting ofthe pumping unit, and this steam exerts a force against the turbinewheel to effectively counterbalance the starting thrust load of thepumping unit.

The novel adaptation of the turbine elements to counterbalance startingthrust load of the pumping unit as described above will be betterunderstood when considered in connection with the accompanyingspecification and the drawing forming a part thereof.

In the drawing, a partly broken away longitudinal section of a steamturbine driven pump unit is shown which embodies the present invention.

More particularly, in the drawing, the pump designated 1, and the steamturbine designated 2, are shown suitably mounted on a common rotatableshaft 3 so that the turbine wheel when driven by steam will in turndrive the pump impeller 5. The fluid to be pumped enters the pump 1through its inlet 6, and prior to starting of the pumping unit, thisfluid contained in the inlet 6 will cause a thrust load on the shaft Sinthe direction of the arrow A. More specifically, this thrust load atstarting is due to the static pressure of the fluid, which pressure maybe about 2000 p. s. i. (pounds per square inch) and cause a thrust loadof between 20,000 to 30,000 pounds on the shaft 3.

Situated to the right of the turbine 2, and suitably mounted about theshaft 3 to provide support to the shaft 3 against thrust, is a suitabletype thrust bearing, generally designated 7 and shown onlydiagrammatically in the drawing. This bearing 7 is of the well knownKingsbury type and thus its construction and operation does not need tobe more fully described herein, and is selected solely in accordancewith its thrust load carrying capacity during operation of the pumpingunit. In other words, the selection of the bearing is made independentof the consideration that it must overcome the large starting thrustload as hereinbefore mentioned, and therefore the bearing 7 is notlarger in size or more expensive than is needed for normal operationalthrust load requirements of the pumping unit.

To accomplish this economy in the selection of the bearing 7, suitablemeans, to be fully described, are provided in the pumping unit tocounterbalance and thus efiectively eliminate the starting thrust loadthat would ordinarily be imposed on the said bearing prior to startingof the pumping unit.

These means generally consist of the usual elements of the turbine 2,arranged in their usual functional positions within the said turbine,and specifically adapted to the purpose of counterbalancing axial thrustin accordance with the teachings of the present invention. Thus, it willbe noted that the turbine wheel 4 is disposed to rotate within the steamchamber 8 formed by the bell-shaped turbine casing 9 and the end plate10 mounted to this said casing by the bolt means 11, and so of necessitythe turbine wheel 4 has running clearance on either side, between it andthe steam chamber walls.

Suitably mounted about the periphery of the turbine wheel 4 are two rowsof steam buckets 12, between which is an intervening row of redirectingblades 13 carried on a ring element l lmounted to the end plate 10 bythe bolt means 15. Axially adjacent the right row of steam buckets 12are the flow directing nozzles 16 which are circumferentially spacedwithin a ring element 17 connected to the end plate 10 by the bolt means18. Thus, steam enters the turbine 2 through an inlet conduit 19, fillsan annular chamber 20, and then is directed through the nozzles 16 alonga 360 degree arc of steam admission to the steam buckets 12, the steamthen expands in the said buckets to drive the turbine wheel 4, andfinally is exhausted through the turbine steam outlet conduit 21. Itwill be appreciated that in order to obtain maximum efficiency from thesteam turbine 2, the flow directing nozzles 16 must be in closeproximity to the right row i of steam buckets 12 along the 360 degreeare of steam admission. For this reason, the clearance space betweenthis row of buckets 12 and the nozzles 16 usually does not exceed .030inch.

It has been found that this small clearance space between the right rowof buckets 12 and the nozzles 16 constitutes a natural restriction toany steam that attempts to fiow radially outwardly from the runningclearance space on the right side of the turbine wheel 4. Thus, thisclearance space is in effect a usable steam chamber, being hereindesignated 22, and defined on one side by the right side 23 of theturbine wheel 4, on the other side by the Wall section 24 of the endplate 10, and on the end generally by the right row of buckets 12 andthe nozzles 16, or more particularly by the circular rim 25 formed inthe end .of .the turbine wheel 4 carrying the right row of buckets 12and the ring element 17 containing the nozzles 16.

As clearly shown in the drawings, a suitable inlet 26 is provided to thesteam "chamber ,22, which inlet in practice is connected to atsuitablesource of .high pres sure steam ,(notrshown). Thus, prior to starting ofthe pumping innit, high pressure steam is admitted through therinlet '26to the steam chamber 122, and in thischamber the said steamcxerts aforceagainst ,theturbine wheel 4 in the directionof the arrow B. 'l'hisforceexerted by the said steam against the turbine wheel 4 thuscounterbalances the starting axial thrust load caused by thestaticpressure of the fluid within the pump .inlet 6 and :thus accomplishesthe objects of the gpresent invention.

It will be ,underst00d1that the invention is :not to be limited to thespecific construction or arrangement ,of partsshown, butthat they maybewidely modified within the invention, as rdefined byythel claim.

"Whatjs claimed is: I

:In a steam turbine including, a casing rhaving L3- steam chamber formedtherein, :a turbine wheel disposed for rotation 'within said steam:chamber, a row :of steam bucketscarried about the periphery of saidturbine wheel,

and circumferentially spaced flow directing nozzles in proximate spacedrelation to the steam buckets mounted about the interior of the wall ofsaid steam chamber, the combination with said turbine of means forcounterbalancing an axial force exerted against the side of the turbinewheel remote from the flow directing nozzles, said means comprising anannular chamber formed in the steam chamber on the side of the turbinewheel nearest the flow directing nozzles, said annular chamber definedon oneside bythe side of the turbine wheel, on the other side .by the,wall of the steam chamber, and on the end by the buckets and .fiowdirecting nozzles in proximate spaced relation to each other, and aninlet to said annular chamber communicating with a suitable source ofpressurized steam, whereby steam admitted to said annular chamber willexertra ,counterbalancing force against the said turbine wheel.

References Cited in the file of this patent UNITED STATES PATENTS892,559 'Pfau Sept. 29, 1908 1,030,153 :Barbezat June 18, 1912 1,610,454Lawaczeck Aug. 29, 1921 2,746,671 Newcomb May 22, 1956

